Solar Ready Hot Water Cylinders: Building Consent Explained (NZ)
Adding solar hot water — or making a cylinder “solar ready” — usually involves roof work, plumbing, and sometimes electrical changes, so building consent is often required. The rules here are the existing Building Code requirements, not a new mandate. This guide sets out when consent is needed, which standards apply, and where a like-for-like replacement may be exempt.
Building Consent Requirements
In general, you need building consent for a solar ready hot water cylinder installation that involves structural modifications, roof penetrations, or plumbing and electrical work beyond a simple like-for-like swap. A council (building consent authority) has a statutory 20 working days to process a complete application.
Consent — the essentials
Which Systems Require Consent
Installations involving new cylinder mounting, roof penetrations, or electrical upgrades generally require consent. A straightforward cylinder replacement using existing connections may be exempt under Schedule 1 of the Building Act — but adding solar collectors or new roof penetrations usually takes the job outside that exemption.
Compliance Standards
Solar water heating installations are covered by the plumbing and drainage standard AS/NZS 3500.4 (heated water services), alongside the manufacturer’s installation instructions and the Building Code. Copies of the standards can be purchased from Standards New Zealand.
Building Code Requirements
Installations must meet Building Code clause G12 (Water Supplies) and, for any roof penetrations, clause E2 (External Moisture). The system also needs adequate pressure and temperature relief provisions in line with G12.
Pre-installation Documentation
A consent application typically includes the manufacturer’s specifications, structural details for the roof mounting, and the relevant plumbing and electrical documentation. Remember the council has up to 20 working days to process a complete application.
Exemption Categories
Limited exemptions apply to:
- Like-for-like replacement using existing mounting points and connections
- Minor work that does not involve structural changes or new roof penetrations
- Work covered by an existing consent, or specific Schedule 1 exemptions
Council Inspection Requirements
Where consent is required, the council will usually inspect at rough-in (plumbing and electrical) and again at final, before issuing the code compliance certificate (CCC). Some councils accept remote or photo inspections for straightforward work.
Retrofit Considerations
On an existing home, the roof may need a structural check to confirm it can carry the collector and cylinder loads. Mains-pressure cylinders also need proper seismic restraint under the Building Code — this applies to cylinders generally, not just larger ones.
